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can't see layer in ArcMap   Heather Basara Dec 15, 2005
Re: can't see layer in ArcMap   Dan Patterson Dec 15, 2005
Re: can't see layer in ArcMap   Heather Basara Dec 15, 2005
Re: can't see layer in ArcMap   Melita Kennedy Dec 16, 2005
Re: can't see layer in ArcMap   Heather Basara Dec 19, 2005
Re: can't see layer in ArcMap   Melita Kennedy Dec 19, 2005
Re: can't see layer in ArcMap   Heather Basara Dec 20, 2005
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Subject can't see layer in ArcMap 
Author Heather Basara 
Date Dec 15, 2005 
Message Hi,

I have a shapefile that I changed the projection and coordinate system so it would match some other data. Following these changes I added the layer to ArcMap (v9), and although the layer shows up under the data layer column, nothing can be found in the map area. I "zoomed to layer", selected the "full extent" and still see nothing. In data properties, things look right, so I am bewildered why I can't see the layer. Any thoughts?

Thank you. 
   
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Subject Re: can't see layer in ArcMap 
Author Dan Patterson 
Date Dec 15, 2005 
Message start a new project, and add just that data layer and inspect its coordinates on-screen to see if they were inappropriately defined 
  Geomatics, Carleton University, Ottawa, Canada 
   
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Subject Re: can't see layer in ArcMap 
Author Heather Basara 
Date Dec 15, 2005 
Message I started a new project and added the layer. This time there was a warning for an "inconsistent extent". I haven't had this before. What do I do with this (I'm guessing its the source of my trouble). Thank you! 
   
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Subject Re: can't see layer in ArcMap 
Author Melita Kennedy 
Date Dec 16, 2005 
Message Hi,

Changing the coordinate system in ArcCatalog (or using the Define Projection tool in ArcToolbox) updates the metadata information only. It doesn't update the actual data coordinate values. The dataset now has an incorrect coordinate system. If the data frame is not in the same (wrong) coordinate system, ArcMap is trying to project the data on-the-fly to the new system. BEcause the input values aren't correct, the output ones are probably being clipped out as not valid for the coordinate system.

The warning message you're getting, "inconsistent extent", is another clue. "Inconsistent extent" is displayed if a dataset has a defined geographic coordinate system (latitude-longitude) but has an extent with values that are too large for decimal degrees.

Redefine the data back to its original coordinate system. If you want, reproject it to a new dataset in the coordinate system you want to use.

Melita Kennedy
ESRI Product Specialist 
  Melita Kennedy
ESRI Product Specialist 
   
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Subject Re: can't see layer in ArcMap 
Author Heather Basara 
Date Dec 19, 2005 
Message Hi,

I have reprojected the data back to the original coordinate system as you suggested. I would like to reproject it to a new data set in a different coordinate system (essentially go from NAD_83_utm_18N / GCS_North_American_1983 which looks like Lat/long to GCS_North_American_1983 which looks like utm coordinates).

I have used the ArcToolbox and followed these steps:

Projections & Transformations
1. Define Projection: selected shapefile (input dataset or feature class)
2. Select coordinate system (GCS_North_American_1983)
3. OK

Projections & Transformations
1. Feature
2. Project
a. select layer that I just worked on (part a above)
b. Select ouput coordinate system
c. Projected coordinate systems: utm: nad83: nad 83 utm zone 18N
d. Apply, then OK
e. select OK on Project dialog box.

I'm not sure if I need the NAD 83 or if this is where my problems are being caused. Essentially I just need all of the data to be utm for the analysis I have to run. How do I do this?

Thank you!

 
   
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Subject Re: can't see layer in ArcMap 
Author Melita Kennedy 
Date Dec 19, 2005 
Message Hi Heather,

These steps look correct.

Lat/lon data is always based upon some geographic coordinate system (aka datum - which is part of a gcs). Change the gcs, and the coordinates for a point will usually change. In fact, if you have UTM data in the mainland US and you mistake the gcs part--call it NAD27 when it's really NAD83, or vice versa--the UTM coords can be as much as 200 meters off.

Before, the data was lat/lon (gcs) but you defined the metadata information as UTM. That causes the data to show in really the wrong location!

Melita
 
  Melita Kennedy
ESRI Product Specialist 
   
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Subject Re: can't see layer in ArcMap 
Author Heather Basara 
Date Dec 20, 2005 
Message Hi Melita,

I have followed the steps I sent you earlier, but when I have done so the lat/long doesn't change (even in the metadata). Is there a reason why not?

The layers all appear to have consistent definitions of GCS_N_A_83 and projected NAD_83_utm_zone18n. Some show coordinates in utm and others show up in lat/long still. What am I missing?

Thanks for your patience and help!

Heather